Canon going to leapfrog the sigma in IQ... how much wishful thinking is this, how much "better" do you think Canon's will be?.... oh, right... the "colors" and "bokeh" will all be $1000 better like all the other L lenses compared to the competition. And will probably be sharper at F/1.4 than the siggy is at F/2.8 right?
My guess is that it would be marginally better than the Sigma, but certainly not worse. Heck, if it could merely match the Sigma IQ and not have the onion bokeh I'd say that would be a pretty swell lens!
As for the recent trend of L lenses... what, more like the 24-70 F4L or F2.8LII? Because the F4L is trash and costs a fortune.
I hope that's a rhetorical question! But it's a fair one, and to be perfectly honest since picking up the 24-70mm ii I forget that "other" new 24-70 L even exists. With that one exception, I have to go back to the 16-35 ii to find a top-level EF lens that has been even modestly disappointing on my radar in the past half-decade or so. Of course, I can't speak for those renting/buying super-teles, but I read mostly good things about those recent releases too.
5D mark 3: R14/2.8, 24mm f/2.8 IS, 35mm f/2 IS, 50 1.2L, 100L macro, 85L, 135L, 300mm f/2.8 ii. 8-15L Fisheye, 16-35L, 24-70L II, 70-200L IS II, TAM 150-600mm, 2x600ex-rt
EOS M: 18-55mm, 22mm
SL1: 10-18mm IS, 18-55mm IS